This invention relates to a method and apparatus for separating sheet material, such as paper, from a stack and can be used in automated document processing equipment such as high speed accumulators or counters.
One of the problems that must be solved in order to build a successful automated document processing line, such as an envelope inserter or a binder, is an ability to separate and combine all of the sheets of a document into a group. Prior to separation, these sheets could have gone through printing, laminating or other processes and were accumulated into a large contiguous stack. Thus, it is necessary to separate predetermined number of sheets stacked, one after another, to form a complete document.
The most simple methods are performed by the means of friction or vacuum rollers, where single sheets are separated from the stack and then directed one at a time into a receiving device or accumulator. The number of separated and then directed sheets for assembly into a group is counted by the use of mechanical, optical, or other sensors. See, for example, the sheet separation in the apparatus of U.S. Pat. No. 4,222,556, Chapman et al., 1980. This single sheet separation yields high quality control of the quantity of individual sheets but drastically reduces the performance of an automated line.
Better performance can be achieved if separated sheets, directed into a receiving device, are overlapped or displaced against each other, as disclosed in U.S. Pat. No. 3,635,463 to A. Stobb, 1972 or U.S. Pat. No. 4,204,667 to E. Klenk, 1980.
In the known apparatus of U.S. Pat. No. 3,635,463, sheets from the stack are separated by the use of a rotating brush that pushes sheets at their edges. Separated sheets are transported to a receiving device where the quantity is determined by the measurement of the thickness of the accumulated group by the use of a sensor.
In the apparatus of U.S. Pat. No. 4,204,667, the sheets from the stack are offset by the transport with a narrow gap, and the quantity of sheets is determined by measuring the thickness of accumulated groups in assembly station.
Greater performance could be achieved if the quantity of sheets that are separated from the stack is predetermined and directed to a receiving device so that a block of predetermined number of sheets is delivered to the receiving device. In the known apparatus of U.S. Pat. No. 4,986,731 to T. Shinomiya, 1991, a predetermined quantity of sheets is separated from the stack by the use of the following method. Initially, the block is offset or partially separated in reference to the stack by the use of the special lever. Next, the block is thrown to the moving transport and arrives at a receiving device. The quantity of pages is determined by the depth of an offset lever that moves along the edge of the stack. High performance could be achieved by realizing this known patent. However, such performance will require the use of an extremely high precision mechanical device which, under high production conditions, is very difficult to implement and does not solve the problem of controlling the precise quantity of pages in a separated block.